Q/BQB 419-2023 English PDF

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Q/BQB 419-2023: Cold-rolled conventional high strength steel sheet and strip
Q/BQB 419-2023
BQB®
ENTERPRISE STANDARD OF
BAOSHAN IRON and STEEL CO., LTD.
Replacing Q/BQB 419-2021
Cold-rolled conventional high strength steel sheet and strip
ISSUED ON: APRIL 09, 2023
IMPLEMENTED ON: JULY 01, 2023
Issued by: Baoshan Iron and Steel Co., Ltd.
Table of Contents
Foreword ... 3
1 Scope ... 5
2 Normative references ... 5
3 Terms and definitions ... 6
4 Category and code ... 7
5 Information required for ordering ... 8
6 Dimensions, shape, weight, tolerance ... 9
7 Technical requirements ... 9
8 Inspection and test ... 14
9 Packaging, marking, inspection documents ... 15
10 Numerical rounding rules ... 15
11 Approximate comparison of designations ... 15
Appendix A (Informative) Comparison of similar designations between this document
and relevant domestic and foreign standards ... 16
Cold-rolled conventional high strength steel sheet and strip
1 Scope
This document specifies the terms and definitions, classification and code, size, shape,
weight, technical requirements, inspection and test, packaging, marking and inspection
documents of cold-rolled conventional high-strength steel sheets and strips.
This document applies to cold-rolled conventional high-strength steel sheets and strips
(hereinafter referred to as steel sheets and strips), which have a thickness of 0.40 mm ~
3.5 mm, as produced by Baoshan Iron and Steel Co., Ltd.
2 Normative references
The contents of the following documents constitute the essential provisions of this
document through normative references in the text. Among them, for the dated
documents, only the versions with the dates indicated are applicable to this document;
for the undated documents, only the latest version (including all the amendments) is
applicable to this standard.
GB/T 222 Method of sampling steel for determination of chemical composition and
permissible variations for product analysis
GB/T 223 Methods for chemical analysis of iron, steel and alloy
GB/T 228.1-2021 Metallic materials - Tensile testing - Part 1: Method of test at room
temperature
GB/T 2523 Measuring method of surface roughness, peak count and waviness for
cold-rolled metal sheet and strip
GB/T 2975 Steel and steel products - Location and preparation of samples and test
pieces for mechanical testing
GB/T 4336 Carbon and low-alloy steel - Determination of multi-element contents -
Spark discharge atomic emission spectrometric method (routine method)
GB/T 5027 Metallic materials - Sheet and strip - Determination of plastic strain ratio
GB/T 5028 Metallic materials - Sheet and strip - Determination of tensile strain
hardening exponent
GB/T 8170 Rules of rounding off for numerical values and expression and judgement
of limiting values
GB/T 20066 Steel and iron - Sampling and preparation of samples for the
determination of chemical composition
GB/T 20123 Steel and iron - Determination of total carbon and sulfur content
Infrared absorption method after combustion in induction furnace (routine method)
GB/T 20125 Low-alloy steel - Determination of multi-element contents -
Inductively coupled plasma atomic emission spectrometric method
GB/T 20126 Unalloyed steel - Determination of low carbon content - Part 2: Infrared
absorption method after combustion in an induction furnace (with preheating)
GB/T 24174 Steel - Determination of bake-hardening-index (BH2)
Q/BQB 400 Package mark and inspection document for cold-rolled product
Q/BQB 401 Dimension, shape, weight and tolerances for cold-rolled steel sheet and
strip
3 Terms and definitions
3.1 Rephoshorized steels (P)
In low carbon steel or ultra-low carbon steel, the strength of steel is mainly increased,
by adding solid solution strengthening elements, such as phosphorus, which does not
exceed 0.12%. This steel has high strength and good cold-forming properties, as well
as good impact resistance and fatigue resistance; it is usually used in the production of
automotive panels and structural parts.
3.2 High strength interstitial free steels (Y)
The plastic strain ratio (r value) and strain hardening exponent (n value) of the steel are
improved, by controlling the chemical components in the steel. Due to the solid solution
strengthening of the elements in the steel and the interstitial free microstructure, this
steel combines high strength with very good cold formability; it is usually used to make
complex parts, that require deep drawing.
3.3 Bake hardening steels (B)
A certain amount of solid solution carbon and nitrogen atoms are retained in the steel,
meanwhile strengthening elements such as phosphorus and manganese can be added to
increase the strength. After processing and forming, after baking at a certain
temperature, the yield strength of the steel is further increased due to age hardening. It
is typically applied to automotive exterior panels.
Note: Usually, the date of issue in the product inspection document is specified as the date of
completion of the manufacture of the product.
7.4 Mechanical properties
7.4.1 The supplier guarantees that within 6 months from the date of completion of
manufacture, the mechanical properties of steel sheets and strips shall comply with the
corresponding provisions in Table 5, Table 6, Table 7.
7.4.2 When steel sheets and steel strips are supplied as specified parts, the supplier and
the purchaser can agree on a range of mechanical properties, that meets the processing
requirements of the parts, as the acceptance benchmark. At this time, the mechanical
properties, which are specified in Table 5, Table 6, Table 7, will not be used as a basis
for delivery.
7.4.3 Due to the influence of aging, the mechanical properties of steel sheets and steel
strips will deteriorate, with the prolongation of storage time, such as the increase of
yield strength and tensile strength, the decrease of elongation at break, the deterioration
of formability, the appearance of tensile strain marks, etc. So, it is recommended that
users use it as soon as possible.
7.5 Tensile strain marks
7.5.1 The requirements for tensile strain marks are only applicable to steel sheets and
strips, which have the surface quality requirements of FC and FD, under room
temperature storage conditions.
7.5.2 If the temperature of the storage place can be guaranteed to be below 50 °C, the
high-strength rephoshorized steels shall be guaranteed to have no tensile strain marks,
when used within 3 months from the date of completion of manufacture; the high-
strength bake hardening steels shall be guaranteed to have no tensile strain marks, when
used within 6 months from the date of completion of manufacture.
7.5.3 For the high-strength interstitial free steel and high-strength isotropic steel, it shall
ensure that no tensile strain marks appear, during use within 6 months from the date of
completion of manufacture.
7.5.4 Under some service conditions, high-strength low-alloy steel (LA) may have the
risk of tensile strain marks, which can be determined through negotiation, if the user
has special requirements.
Note: The single measurement length cutoff is generally selected as 0.8 mm. If it chooses 2.5 mm or other lengths,
it shall be specified in the contract.
7.7.2 Surface structure suitable for environmental coating (BAOTEXTM)
BAOTEXTM products can meet the technical requirements of advanced environmental
protection coating technology. If users have needs, they can be negotiated when
ordering.
7.7.3 Surface ...